Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!usc!wuarchive!uunet!mcsun!unido!uniol!Ingo.Wilken
From: Ingo.Wilken@arbi.informatik.uni-oldenburg.de (Ingo Wilken)
Newsgroups: comp.sys.amiga.misc
Subject: Re: Bitfields in C
Message-ID: <ingo.673701671@faramir>
Date: 8 May 91 11:21:11 GMT
References: <214.2826444A@weyr.FIDONET.ORG>
Organization: University of Oldenburg, Germany
Lines: 33

David.Plummer@p0.f70.n140.z1.FIDONET.ORG (David Plummer) writes:
>Does anyone know how to build an easily- addressable bitfield array in 
>C?  Exactly what I would like to be able to do it this:                
>struct bits {                                                          
>   unsigned long thebits[31] : 1;                                      
>}                                                                      
>which of course is impossible, since C doesn't allow arrays in the     
>bitfield descriptors.                                                  
[...]
>does anyone have any suggestions?

What about this:
    struct bits { unsigned int thebits:31; };

If you want to set bit 10, you just do something like

    struct bits i;
    i.thebits = 0;

    i.thebits |= (1<<10);

and a check if bit 7 is set would be

    if( i.thebits & (1<<7) )
       printf("Yeah!\n");

Hope this helps.
Ingo
-- 
Ingo Wilken, CS Student, Univ.of Oldenburg, FRG | "Sie kennen das ja vom Pro-
wilken@uniol.uucp (..!uunet!unido!uniol!wilken) |  grammieren, man weiss ja
Ingo.Wilken@arbi.informatik.uni-oldenburg.de    |  nicht was die Dinger tun."
wilken@uniol.zer   IRC:Nobody   OL:ingo@faramir +--------------- Prof. Claus